The present invention relates to a video network server, and more particularly, to a video network server which selects a data transfer method or sets various parameters in accordance with status of a network system in a video network system for distributing sound/video image information to terminals.
In recent years, with a progress of an image compression technology or a high-speed digital network technology, a wide variety of multimedia systems are increasingly constructed. In order to construct a multimedia network system by combining various equipments using a general computer and operate it smoothly, there is a need for a function for setting various parameters such as a time slot period and a time slot size or a number of allowable terminals according to status of the system and a function for reconstructing the system by resetting these various parameters in accordance with change of status.
A description is given of time slot management of the video server which decides setting of parameters with reference to FIG. 35. Since it is difficult to distribute data to each terminal in a given ratio in a network system including a plurality of terminals only by reading and transferring the data sequentially, particularly in the case by using motion picture data of a large capacity, a time slot management method wherein data is sent to each terminal periodically for a given time is generally employed in the video network server. As shown in FIG. 35, the video server divides a given time interval, i.e, a time slot period uniformly and allocates the divided given time interval to each terminal. The time allocated to each terminal in a time slot period is a time slot size. The video server reads and transfers data to each terminal for each time slot size, thereby distributing data to a plurality of terminals in a given ratio. As shown in FIG. 35, data is sequentially read and transferred for each time slot size as follows: data A1 to a terminal Axe2x86x92data B1 to a terminal Bxe2x86x92data C1 to a terminal C (one time slot period)xe2x86x92data A2 to the terminal A . . . . Conventionally, a time slot period and a time slot size are decided when parameters are set in the video server and then, on the basis of the time slot period and the time slot size, a number of allowable terminals or a response speed, i.e., the other parameters are decided.
A description is given of a function for setting various parameters for operating a system in a video net work server which distributes sound/video image information or the like to a plurality of terminals employed conventionally with reference to figures.
FIG. 34 is a diagram illustrating a prior art video network server. In the figure, a parameter computing means 901 is for computing parameters in accordance with a construction of a system. The construction of the system includes a number or performance of storage devices such as connected disks, or a capacity of a memory mounted in the system, for example. A parameter computation information holding means 902 is for holding information with which the parameter computing means 901 computes parameters. A parameter setting means 903 is for setting the parameters computed by the parameter computing means 901 in the system. Actually, various components such as a system construction checking means for checking the construction of the system are necessary, and are dispensed with herein.
The prior art server constructed above operates as follows in setting parameters. The parameter computation information holding means 902 holds information as to the construction of the system such as a type and a number of disks as storage devices or a capacity of a memory, or information for setting parameters such as a formula for computing parameters on the basis of the former information. The parameter computing means 901 computes parameters such as the time slot period and the time slot size in the time slot management mentioned above or the number of allowable terminals or the transfer speed in view of performance in accordance with the construction of the system, on the basis of the information which is held by the parameter computation information holding means 902. The parameter setting means 903 sets the parameters which are computed by the parameter computing means 903 in the system.
The video network system is operated according to thus set parameters, and when the construction and status of the system change, parameters are reset following the procedure.
In the prior art server, when parameters are computed or set, it is possible to compute and set appropriate parameters in view of factors determined by the constructions of the system such as the number or performance of disks, but it is difficult to compute and set appropriate parameters in view of external and dynamic factors such as change of network operating form or change of network traffic (congestion). Therefore, if performance of the system with parameters initially set is degraded due to changes of the external factors, the system is operated without changing initialization, so that status of the network becomes worse than predicted and the server is overloaded, causing damaging effects on use of data. On the other hand, when status of the network is more preferable than predicted, performance of the system is degraded without making the best use of a reserve power of the system.
In the former case in which status of the system becomes worse than predicted, when traffic of the network increases or the network server is overloaded in reproducing motion picture data at the terminal, discontinuity of sound of data occurs or response of the server becomes worse, causing stop of reproduction.
In this case, since response of the server is worse than predicted, changing parameters of the system which decides response speed such as making the time slot period shorter than normal, limiting the number of allowable terminals must be performed, or when operating status is worse than described above, which is difficult to cope with by changing parameters, it is difficult to avoid the adverse effects without taking actions for reducing load of the server, such as performing switching of a method of obtaining data so as to transfer all data to terminals and reproduce the data at the terminals. As the method of obtaining data, a method wherein terminals receive data which is reproduced by the server itself using NFS protocol, for example, is less burdensome and desirable to the terminals. However, when status of the server or the network is worse and the adverse effects occur, it is desirable to transfer all data to the terminals and reproduce the data at the terminals using FTP protocol, since discontinuity of data is avoided.
In the latter case, the reserve power of the server is not made the best use of if status of the network is more preferable than predicted. For example, when the system is set to transfer all motion picture data to the terminals and reproduce the data at the terminals or the number of allowable terminals is limited severely allowing for congestion of the network or load of the server, it is impossible to reproduce data or to increase terminals to which data is supplied, with the server less overloaded than predicted. In another case, assuming that data requiring a fast transfer rate is used, when a time slot period is set according to its required transfer rate, use of data of required transfer rate which is lower than predicted causes time of no use in a time slot.
In the prior art server, in order to improve the above-described problem which may occur when status of the system changes, the user must interrupt operation of the system consciously and check its status, and then change parameters or various conditions.
In some cases, the user demands that discontinuity of sound or stop of reproduction be avoided with a number of terminals limited, while the user demands that many terminals be used with discontinuity of sound or stop of reproduction occurring in some degree. However, parameters cannot be changed with flexibility depending on allowable qualities in the prior art server system.
It is an object of the present invention to provide a video network work server wherein switching of a method of obtaining data can be performed in accordance with busy status of the network or status of the server in operating the system, thereby data is transferred with reliability and a reproduction quality is improved.
It is another object of the present invention to provide a video network server wherein parameters are changed and a limited number of terminals which the system may allow is changed in accordance with busy status of the network or status of the server in operating the system, thereby data is transferred with reliability and a reproduction quality is improved.
It is still another object of the present invention to provide a video network server wherein a number of allowable terminals can be set in accordance with allowable qualities of data specified by the user in addition to change of parameters according to status of the system, thereby it is possible to set the system with flexibility in operating the system.
It is a further object of the present invention to provide a video network server wherein parameters of the system can be changed and time slot management can be adjusted depending on a transfer rate of data which is requested by each terminal in operating the system, thereby performance of the system is improved.
Other objects and advantages of the invention will become apparent from the detailed description that follows. The detailed description and specific embodiments described are provided only for illustration since various additions and modifications within the scope of the invention will be apparent to those of skill in the prior art from the detailed description.
According to a first aspect of the present invention, a video network server which distributes sound/video image information to a plurality of terminals comprises a network system status obtaining section for obtaining status of a network system including a network server, a network and terminals; a network system status decision section for deciding the status of the network system which is obtained by the network system status obtaining section; a data obtaining method selecting means for selecting a data obtaining method on the basis of a result which is decided by the network system status decision section; and a data obtaining method switching means for performing switching of a data obtaining method when the data obtaining method which is selected by the data obtaining method selecting means is different from a data obtaining method at present.
According to a second aspect of the present invention, the video network server according to the first aspect includes a network status obtaining means for obtaining status of the network as the network system status obtaining section and a network status decision means for deciding the status of the network which is obtained by the network status obtaining means as the network system status decision section.
According to a third aspect of the present invention, the video network server according to the first aspect includes a network server information obtaining means for obtaining information of the network server as the network system status obtaining section and a network server status decision means for deciding status of the network server on the basis of the information of the network server which is obtained by the network server information obtaining means as the network system status decision section.
According to a fourth aspect of the present invention, a video network server which distributes sound/video image information to a plurality of terminals comprise a network system status obtaining section for obtaining status of a network system including a network server, a network and terminals; a network system status decision section for deciding the status of the network system which is obtained by the network system status obtaining section; a parameter computing means for computing parameters including a number of terminals which the system may allow on the basis of a result which is decided by the network system status decision section; and a parameter setting means for setting parameters of the system on the basis of a result which is computed by the parameter computing means.
According to a fifth aspect of the present invention, the video network server according to the fourth aspect includes a network status obtaining means for obtaining status of the network as the network system status obtaining section and a network status decision means for deciding the status of the network which is obtained by the network status obtaining means as the network system status decision section.
According to a sixth aspect of the present invention, the video network server according to the fourth aspect includes a network server information obtaining means for obtaining information of the network server as the network system status obtaining section and a network server status decision means for deciding status of the network server on the basis of the information of the network server which is obtained by the network server information obtaining means as the network system status decision section.
According to a seventh aspect of the present invention, the video network server according to the fourth aspect further comprises an allowable quality specifying means for specifying an allowable range of a quality of reproduced data, the parameter computing means computing parameters of the system including a number of terminals which the system may allow on the basis of the allowable range specified by the allowable quality specifying means.
According to an eighth aspect of the present invention, the video network server according to the seventh aspect includes a network status obtaining means for obtaining status of the network as the network system status obtaining section and a network status decision means for deciding the status of the network which is obtained by the network status obtaining means as the network system status decision section.
According to a ninth aspect of the present invention, the video network server according to the seventh aspect includes a network server information obtaining means for obtaining information of the network server as the network system status obtaining section and a network server status decision means for deciding status of the network server on the basis of the information of the network server which is obtained by the network server information obtaining means as the network system status decision section.
According to a tenth aspect of the present invention, a video network server which distributes sound/video image information to a plurality of terminals comprises a data storage means for storing data; a buffer memory for temporarily storing data to be transferred; a parameter computing means for allocating a given time interval in a period which is allocated for a terminal for another terminal when it is possible to read data which is requested by the terminal in a time that is less than a given time interval in a predetermined period; a data prereading means for reading the data which is requested by the terminal for a given time interval in a period which is allocated by the parameter computing means from the data storage means and outputting the data to the buffer memory; and a data feeding means for feeding the data which is output to the buffer memory to the terminal.
According to an eleventh aspect of the present invention, the video network server according to the tenth aspect wherein, when it is possible to read data which is requested by a terminal in half of a given time interval in a predetermined period, the parameter computing means allocates a given time for the terminal every two periods and a given time interval in a remaining period for another terminal.